Introduction:
Neutral Density filter evenly reduces the amount of light passing through the lens without affecting the color. Ideal for reducing bright light in large aperture situations when a narrow depth field is needed. Neutral Density Filters are often used to achieve motion blur effects with slow shutter speeds.
The light reduction is even across the visible spectrum (or it should be). With less light reaching the imaging sensor, a longer exposure or a wider aperture can be used , which can avoid the effects of diffraction or to achieve a shallow depth of field under even full sunlight.